This invention relates to terminals for cardiac stimulators and, in particular, to implantable heart pacemaker devices.
In implantable heart pacemaker devices, pacemaker leads are connected to a patient's heart for acing or sensing cardiac electrical activity. The pacemaker lead is connected by its proximal end to a terminal on the pacemaker, and the distal end of the lead is disposed in suitable tissue. The precise location of the distal end may depend on factors, such as whether the lead is for sensing heart functions or for pacing such functions.
Existing pacemaker terminal devices, such as the device shown in U.S. Pat. No. 4,445,511 to Cowdery and Cooper, utilize connection of the pacemaker lead to the terminal by means of insertion of the proximal end of the lead into a lead hole in the terminal. The lead is then secured in this position in the terminal by means of screws commonly called "grub" screws.
One problem with pacemaker terminal devices which use grub screws is the inconvenience caused to a physician during implantation of the pacemaker device. It is during surgical implantation that the physician connects the pacemaker lead to the patient's heart and to the pacemaker terminal device. With terminal devices which use grub screws, the physician must first locate a slit at the top of the pacemaker terminal and then locate the screws, which are quite small, within the pacer header. Each grub screw is then screwed into the slit by means of a screwdriver. The screw connects with the pacemaker lead, which is inserted into the lead hole of the pacemaker. The force of the screw thus mechanically secures the pacemaker lead to the terminal.
As a part of this lengthy and tedious process, the screwdriver used to tighten the grub screws must, before insertion into the pacer header, be lubricated with a special lubricant which is supplied by the pacemaker manufacturer together with the lead and the screwdriver. Additionally, a problem sometimes occurs if the physician cannot readily find the exact location of the slit at the top of the pacemaker terminal. A further problem occurs when the grub screw head, which may be hexagon in shape, becomes distorted by excessive force, thereby making it difficult to perform the described procedure. Hence, there can be numerous inconveniences to physicians using the existing terminal devices.
A further problem with the use of grub screws for connecting leads in existing devices is the necessity for a slit for insertion of a screwdriver for screwing a grub screw. Such an opening represents a potential leakage path for the unwanted ingress of body fluids into the pacemaker terminal area. Such fluid leakage could impair proper operation of the pacemaker device.